Specialize breakpoint stubs by set of live registers of the stubs they are intercepting.

runtime/vm/stub_code_arm.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 28 matching lines @@
 void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
   const intptr_t isolate_offset = NativeArguments::isolate_offset();
   const intptr_t argc_tag_offset = NativeArguments::argc_tag_offset();
   const intptr_t argv_offset = NativeArguments::argv_offset();
   const intptr_t retval_offset = NativeArguments::retval_offset();
   const intptr_t exitframe_last_param_slot_from_fp = 2;
 
   __ mov(IP, Operand(0));
   __ Push(IP);  // Push 0 for the PC marker.
   __ EnterFrame((1 << FP) | (1 << LR), 0);
-  __ SmiUntag(R4);
 
   // Load current Isolate pointer from Context structure into R0.
   __ ldr(R0, FieldAddress(CTX, Context::isolate_offset()));
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
   __ StoreToOffset(kWord, SP, R0, Isolate::top_exit_frame_info_offset());
 
   // Save current Context pointer into Isolate structure.
   __ StoreToOffset(kWord, CTX, R0, Isolate::top_context_offset());
@@ skipping 1463 matching lines @@
   __ Pop(R0);  // Restore argument.
   __ PopList((1 << R4) | (1 << R5));  // Restore arg desc. and IC data.
   __ LeaveStubFrame();
 
   __ ldr(R2, FieldAddress(R0, Function::instructions_offset()));
   __ AddImmediate(R2, Instructions::HeaderSize() - kHeapObjectTag);
   __ bx(R2);
 }
 
 
-void StubCode::GenerateBreakpointRuntimeStub(Assembler* assembler) {
+// R5: Contains an ICData.
+void StubCode::GenerateICCallBreakpointStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ LoadImmediate(R0, reinterpret_cast<intptr_t>(Object::null()));
   // Preserve arguments descriptor and make room for result.
+  __ PushList((1 << R0) | (1 << R5));
+  __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
+  __ PopList((1 << R0) | (1 << R5));
+  __ LeaveStubFrame();
+  __ bx(R0);
+}
+
+
+// R5: Contains Smi 0 (need to preserve a GC-safe value for the lazy compile
+// stub).
+// R4: Contains an arguments descriptor.
+void StubCode::GenerateClosureCallBreakpointStub(Assembler* assembler) {
+  __ EnterStubFrame();
+  __ LoadImmediate(R0, reinterpret_cast<intptr_t>(Object::null()));
+  // Preserve arguments descriptor and make room for result.
   __ PushList((1 << R0) | (1 << R4) | (1 << R5));
   __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
   __ PopList((1 << R0) | (1 << R4) | (1 << R5));
   __ LeaveStubFrame();
   __ bx(R0);
 }
 
+// R5: Garbage or function address.
+// R4: Garbage or raw argument count.
+void StubCode::GenerateRuntimeCallBreakpointStub(Assembler* assembler) {
+  __ EnterStubFrame();
+  __ LoadImmediate(R0, reinterpret_cast<intptr_t>(Object::null()));
+  // Preserve arguments descriptor and make room for result.
+  __ AndImmediate(R5, R5, ~kSmiTagMask);
+  __ SmiTag(R4);
+  __ PushList((1 << R0) | (1 << R4) | (1 << R5));

[Florian Schneider, 2014/06/30 09:00:40]

Why do you need to preserve R4 and R5 here?

[rmacnak, 2014/07/01 01:08:51]

Don't I need to preserve them for the original stub?

save r4/5
load r4/5 with values for runtime call BreakpointRuntimeHandler
call
restore r4/5
jump to original stub (r0)

My test passes if they aren't though..

[Florian Schneider, 2014/07/03 19:56:03]

I don't think so.  When doing a code search for kRuntimeCall I only see one
place where it is used: the call to the IdenticalWithNumberCheck stub. R4 and R5
are not used for anything there.

+  __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
+  __ PopList((1 << R0) | (1 << R4) | (1 << R5));
+  __ SmiUntag(R4);
+  __ LeaveStubFrame();
+  __ bx(R0);
+}
+
 
 // Called only from unoptimized code. All relevant registers have been saved.
 void StubCode::GenerateDebugStepCheckStub(
     Assembler* assembler) {
   if (FLAG_enable_debugger) {
     // Check single stepping.
     Label not_stepping;
     __ ldr(R1, FieldAddress(CTX, Context::isolate_offset()));
     __ ldrb(R1, Address(R1, Isolate::single_step_offset()));
     __ CompareImmediate(R1, 0);
@@ skipping 277 matching lines @@
   const Register right = R0;
   __ ldr(left, Address(SP, 1 * kWordSize));
   __ ldr(right, Address(SP, 0 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM